In consideration of the purpose of use of lettered tapes created by use of the tape printing device it becomes necessary to employ multiple types of print tapes having different tape widths. Meanwhile, from the viewpoint of resource saving, it is desirable that the cassette case can be reused when the print tape in the cassette case is used up. A tape cassette proposed by the present inventors in Japanese Patent Provisional Publication No. HEI07-25123 in consideration of the above requests was designed to have the following composition and strong points: When the print tape in the cassette case is used up, an empty tape unit (whose print tape has run out) stored in the cassette case body can be replaced with a new tape unit to which a brand-new print tape has been set. Multiple types of tape units corresponding to multiple types of print tapes of different tape widths can be stored in a cassette case body of a single type. For this, each tape unit is provided with a tape width differentiation member.